C# คือต้องการเช็คค่าข้อมูลที่เซฟ ไม่ให้ซ้ำกับข้อมูลในดาตาเบสคับ

private void cmdSave_Click(object sender, EventArgs e)
{
if (MessageBox.Show("คุณต้องการบันทึกใช่หรือไม่", "ยืนยันการทำงาน", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == System.Windows.Forms.DialogResult.Yes)
            {
                tr = Conn.BeginTransaction();

                string CHID;
                string CName;
                string CWID;
                string CTel;
                string CStrart;
                string CWorkage;
                string CTimeIn;
                string CTimeOut;                
                string sqlSave;
                try
                {

                    for (int i = 0; i <= dgvHumanList.Rows.Count - 1; i++)
                    {
                        if (dgvHumanList.Rows[i].Cells["ColIn"].Value != null)
                        {
                            CHID = dgvHumanList.Rows[i].Cells["ColHID"].Value.ToString();
                            CName = dgvHumanList.Rows[i].Cells["ColName"].Value.ToString();
                            CWID = dgvHumanList.Rows[i].Cells["ColPosition"].Value.ToString();
                            CTel = dgvHumanList.Rows[i].Cells["ColTel"].Value.ToString();
                            CStrart = dgvHumanList.Rows[i].Cells["ColStart"].Value.ToString();
                            CWorkage = dgvHumanList.Rows[i].Cells["ColWorkAge"].Value.ToString();
                            CTimeIn = dgvHumanList.Rows[i].Cells["ColIn"].Value.ToString();
                            CTimeOut = dgvHumanList.Rows[i].Cells["ColOut"].Value.ToString();
                            // MessageBox.Show(CWID);
                            // sb = new StringBuilder();
                            sb.Remove(0, sb.Length);
                            sb.Append("INSERT INTO Humanschedule(Date,HID,WorktypeName,Time_IN,Time_OUT)");
                            sb.Append(" VALUES(@Date,@HID,@WorktypeName,@Time_IN,@Time_OUT)");
                            sqlSave = sb.ToString();

                            com.Connection = Conn;
                            com.CommandText = sqlSave;
                            com.Transaction = tr;
                            com.Parameters.Clear();
                            com.Parameters.Add("Date", SqlDbType.DateTime).Value = datework.Value;
                            com.Parameters.Add("HID", SqlDbType.NVarChar).Value = CHID;
                            com.Parameters.Add("WorktypeName", SqlDbType.NVarChar).Value = CWID;
                            com.Parameters.Add("Time_IN", SqlDbType.NVarChar).Value = CTimeIn;
                            com.Parameters.Add("Time_OUT", SqlDbType.NVarChar).Value = CTimeOut;
                            com.ExecuteNonQuery();
                        }
                    }
                    tr.Commit();
                    MessageBox.Show("บันทึกเรียบร้อย", "ผลการทำงาน", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    
                }
                catch 
                {
                    tr.Rollback();
                    MessageBox.Show("คุณได้กำหนดตารางงานของวันนี้ไปแล้ว", "ผิดพลาด", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                }


             }
        }